A rescue robot can not directly find the target which is in other rooms or invisible places by using visual, ultrasonic or infrared ray sensors, because of the smoke or collapsed walls. According to the diffraction property of audio signal, the sound can bypass obstacles. To find the survivors which are often in far field, an audio-based robot localization system is developed to make it feasible to guide the robot run to the target shouting for help. And ideal effects are obtained in experiments.